The present invention relates to solid-state imaging apparatus having a concurrent shutter (hereinafter referred to as global shutter) function.
Conventionally, XY-addressing read methods are generally used to read pixel signals in MOS solid-state imaging apparatus. The construction of MOS solid-state imaging apparatus and XY-addressing read method thereof will be described below by way of FIGS. 1, 2 and 3. FIG. 1 shows a common pixel construction to be used in a MOS solid-state imaging apparatus. What is denoted by numeral 600 in FIG. 1 is a single pixel. Shown respectively therein are: 606, a photodiode serving as photoelectric conversion device; 602, a transfer transistor for transferring signal charge generated at photodiode 606 to a memory 605; 601, a reset transistor for resetting the memory 605 and photodiode 606; 604, an amplifier (amplification transistor) for amplifying and reading voltage level of the memory 605; and 603, a select transistor for selecting the pixel to transmit an output of the amplifier 604 to a vertical signal line 614. Here, those components but photodiode 606 are shielded from light.
Also referring to FIG. 1, denoted by numeral 610 is a pixel power supply, electrically connected to drain of the amplifier 604 and drain of the reset transistor 601. 611 is a reset line for resetting pixels corresponding to one row, which is electrically connected respectively to the gates of reset transistor 601 of the pixels corresponding to one row. 612 is a transfer line for transferring signal charge of the pixels corresponding to one row to the memory 605 of the respective pixels, which is electrically connected respectively to the gates of transfer transistor 602 corresponding to one row. 613 is a select line for selecting pixels corresponding to one row, which is electrically connected respectively to the gates of select transistor 603 corresponding to one row. Use of the pixel construction having four transistors in this manner (hereinafter referred to as 4-Tr pixel) achieves a photoelectric conversion function, reset function, amplification/read function, temporary memory function, and select function.
FIG. 2 shows a general fundamental construction of the solid-state imaging apparatus using the XY-addressing read method. A light receiving section is constituted by a pixel array 700 where pixels 600 having the pixel construction shown in FIG. 1 are arrayed in m-rows by n-columns. A vertical scanning circuit 704 scans the pixel array 700 while outputting to the pixel array 700 a row select signal φSELi (i=1, 2, 3, . . . m), row reset signal
φRSi, and row transfer signal φTXi. At this time, the row select signal φSELi is transmitted to the gate of select transistor 603 of the pixels of i-th row through the select line 613, row reset signal φRSi is transmitted to the gate of reset transistor 601 of the pixels of i-th row through the reset line 611, and row transfer signal φTXi is transmitted to the gate of transfer transistor 602 of the pixels of i-th row through the transfer line 612.
When signals of the pixels of i-th row are to be read out, row select signal φSELi of i-th row is inputted to the pixel array 700 from the vertical scanning circuit 704. When photodiodes 606 of the pixels of i-th row are to be reset, row reset signal φRSi and transfer signal φTXi of i-th row are inputted to the pixel array 700 from the vertical scanning circuit 704. When the memory 605 of the pixels of i-th row are to be reset, row reset signal φRSi of i-th row is inputted to the pixel array 700 from the vertical scanning circuit 704. When signal charge of the pixels of i-th row is to be transferred to the memory 605, row transfer signal φTXi of i-th row is inputted to the pixel array 700 from the vertical scanning circuit 704.
Of the signals of the pixels of selected i-th row, after processing such as the canceling of FPN (fixed pattern noise) at a row parallel processing circuit 701, the results of processing are stored to a line memory 702. Subsequently, scanning and read are effected while sequentially selecting through a horizontal select switch the pixel signals corresponding to one row stored at the line memory 702 by the outputting a horizontal scanning signal φHj (j=1, 2, 3, . . . n) from a horizontal scanning circuit 703. By sequentially effecting this processing from the first row to m-th row, the signals of all pixels of the pixel array 700 can be scanned and read out.
FIG. 3 is a timing chart showing drive timing of the solid-state imaging apparatus of such XY-addressing read method. The drive operation will be described with noticing the time interval of T1. As row select signal φSEL1 is outputted and the reset signal RS1 is then outputted from the vertical scanning circuit 704, pixels of the first row are selected and reset level of the pixels is read out. Further, as row transfer signal φTX1 is outputted from the vertical scanning circuit 704, signal charge generated at the photodiodes 606 of the first row is transferred to the memory 605 so that signal level of the pixels is read out. Subsequently, row reset signal φRS1 and row transfer signal φTX1 are outputted to reset the photodiode 606 and memory 605. The accumulation period of the signal read out here is the time interval indicated by Ta in the figure from immediately after the resetting of photodiode 606 in the previous frame to its transferring. Further, differential processing between the signal level and the reset level is effected during the period of T1, and such signal is stored to the line memory 702. After that, the signals of the first row are outputted by causing an operation of the horizontal scanning circuit 703 to output the horizontal scanning signal φHj (j=1, 2, 3, . . . n). Thereafter similar operation is effected of each row.
In such an ordinary XY-addressing read method (rolling shutter read method), since the point in time for accumulating signal is different from one row to another of the pixel array, or more specifically since a difference in the point in time corresponding to one frame at maximum exists between the first row to be read out first and the m-th row to be read out at the end, a distorted image problem occurs when a rapidly moving object is photographed.
The global shutter read method is provided as a method for solving the above problem in the ordinary XY-addressing read method. Such read method will now be briefly described. FIG. 4 shows drive timing when global shutter operation is effected in a solid-state imaging apparatus having the same fundamental construction as the one shown in FIGS. 1 and 2.
First, as the row reset signals φRS1 to φRSm and row transfer signals φTX1 to φTXm of all the rows are simultaneously outputted from the vertical scanning circuit 704, photodiodes 606 of the pixels corresponding to all rows are reset. Subsequently, after a certain signal accumulation period, row transfer signals φTX1 to φTXm of all rows are simultaneously outputted from the vertical scanning circuit 704. The signal charges accumulated within the certain period at photodiodes 606 of the pixels corresponding to all rows are thereby transferred simultaneously for all rows to the memory 605. By such operation, the global shutter operation is effected.
A row-by-row readout of the signals stored at memory 605 is then started. First, as row select signal φSEL1 is outputted from the vertical scanning circuit 704, the pixels of the first row are selected and the signal level of the pixels are read out. Further, as row reset signal φRS1 is outputted from the vertical scanning circuit 704, the memory 605 of the first row is reset so that the reset level of the pixels is read out. When readout of the signal level and reset level of the pixels of the first row is complete, the pixels of the second row are selected and the signal level and reset level thereof are read out. By effecting this signal read scanning to m-th row, signals corresponding to one frame are read out. Although a horizontal scanning signal φHj of the horizontal scanning circuit 703 has not been shown for ease of explanation, the horizontal scanning signal φHj (j=1, 2, 3, . . . n) is outputted in an interval from the readout of the signals of i-th row to the readout of the signals of i+1-th row.
Japanese Patent Application Laid-Open 2002-320141 for example discloses a solid-state imaging apparatus using 4-Tr pixels, in which global shutter operation is effected.